1. Technical Field
The invention relates to a multi-roll rolling stand whose two work rolls are each supported directly or indirectly via a pair of axially adjustable intermediate rolls on back-up rolls or on supporting rolls arranged in series, each intermediate roll having only one tapered roll barrel end and there being in each case two tapered roll barrel ends on each side of the rolling stand.
2. Description of the Prior Art
It is known that when strips are rolled in a multi-roll rolling stand, the strip edges are subjected to higher pressure than the central regions of the strip, unless countermeasures are taken.
One known countermeasure in multi-roll rolling stands in which, for structural reasons, the work or intermediate rolls cannot simply be bent, as is known in the case of other rolling stands, consists in supporting the work rolls via intermediate rolls over only part of their length rather than over their entire length, the partial length being adjustable.
In a known rolling stand of the type mentioned at the outset (German Patent Specification No. 2,835,514) each work roll is supported on a pair of intermediate rolls. The intermediate rolls are tapered in a similar manner at in each case one end, either conically, parabolically or in another manner, the tapered roll barrel ends of the intermediate rolls associated with different work rolls lying on opposite sides of the rolling stand while the tapered roll barrel ends of the intermediate rolls associated with the same work roll lie on the same side of the rolling stand. By axial displacement of one of the pairs of intermediate rolls and of both pairs of intermediate rolls in a rolling stand of this type, the support length can be adjusted in accordance with the width of the strip to be rolled in such a manner that each edge of the rolled strip overlaps the tapered ends to a greater or lesser extent.
In addition to the adjustment of the intermediate rolls to the edges of the rolled strip, the influencing of the roll nip profile in the central region of the rolled strip is also known in multi-roll rolling stands of this kind. This is achieved by presetting the bearings for supports (saddles) between the support rolls at in each case two back-up rolls, via which the forces associated with rolling are diverted into the one- or two-part housing.
A multi-roll rolling stand of this type has proven its worth over many years in practice; however, the adjustment possibilities for influencing the roll nip profile on such multi-roll rolling stands, namely the axial displacement in pairs of the intermediate rolls having roll barrel ends tapered on one side and the presetting of the bending line at two back-up rolls, are, in many cases, not sufficient to meet the demands commonly made today with respect to the surface evenness of the strips. In particular, it is not possible with such multi-roll rolling stands to carry out an adequate adjustment of the roll nip profile in the region of the strip edges, given the forms of tapering of the roll barrel ends of the intermediate rolls, when the thickness profile of the rolled strip differs greately from strip to strip. The same applies to an abrupt change in the deformation resistance of the material being rolled.
The state of the art also includes two-high, four-high or six-high rolling stands (EP No. 0 049 798 A2), the axially displaceable intermediate or work rolls of which have curved contours running in opposite directions over the barrel length as a whole, these contours complementing one another so as to leave no gaps when the intermediate rolls are in a particular axial position. Rolling stands, the intermediate or work rolls of which have roll barrels contoured in this way are said to make a uniform and continuous alteration of the roll nip profile over the whole length of the roll nip, the influencing of the rolled strip in the edge region being achieved by the known method of roll bending which is possible here.